This invention relates to a printer, in particular, to a printer including a type wheel carrying a multiplicity of fingers carrying types in a plurality of tiers. The type wheel is centrally formed with a rotary shaft and disposed perpendicular to the axis of a platen, wherein a printing operation may be performed by imparting to the type wheel a translational motion to select one of the plurality of tiers or type and a rotary motion for selecting one of the multiplicity of fingers.
In the printer of the type described above, a rotating drive from a drive shaft is normally transmitted to the rotary shaft of the type wheel through an axially translatable universal joint. To select a type located in one of the plurality of tiers, the type wheel must be moved in a direction or a plane perpendicular to the axis of the platen, normally in the vertical direction. A joint which is incapable of axial translation cannot be used since then the type wheel will rock about the joint and cannot be moved in a direction or a plane perpendicular to the axis of the platen. To select one of the multiplicity of fingers by a rotary motion, a controlled angle of rotation of the drive shaft connected to a motor must be precisely transmitted to the rotary shaft of the type wheel. In addition, to provide a compact arrangement, the joint itself must be reduced in size, in particular, its coupling distance must be reduced. Thus, it will be seen that there are a number of requirements imposed upon a joint which is used to provide a connection between the rotary shaft of a type wheel used in a printer and an associated drive shaft.